Preparation of polymer of vinyl benzal acetophenone

ABSTRACT

Light-sensitive polymeric compounds are prepared by condensing a polymer or copolymer containing acyl groups with an aromatic aldehyde of formula QCHO, where Q is an aryl group of the benzene or naphthalene series (substituted or not).  Specified polymers are a  - naphthal -, isopropylbenzal -, p - hydroxybenzal-, p-dimethylaminoo-chlorobenzal-, p-acetamidobenzal-, p-sulphobenzal-, anisal-, and veratral-acetyl benzenes, polyvinylbenzal acetophenone, polyvinylanisal acetophenone and numerous others.  The acylated polymer is preferably a polymer of an acylated vinyl benzene or naphthalene which is then condensed with preferably an excess of the aromatic aldehyde in from about 1/10 to about 25 to 50 mols. of aldehyde per mol. of monomers in the polymers to yield the polyvinyl arylidene acetophenone.  Partially acetylated polystyrene, which may be used, is prepared by treating a carbon disulphide solution of polystyrene with acetyl chloride in the presence of ammonium chloride.  Alternatively an acetylated styrene copolymer may be obtained by copolymerizing a mixture of a vinyl acetophenone (which may be prepared by depolymerizing polyvinylacetophenone) with a compound containing a -CH=C&lt; group, followed by condensing acyl groups of the polymer with the aromatic aldehyde.  This condensation is carried out in the presence of a dehydration catalyst, e.g. sulphuric acid, phosphoric acid, acetic anhydride, phosphorus pentoxide, toluene sulphonic acid, trimethyl benzyl or tetramethyl or tetraethyl, or tetraethanol ammonium hydroxides, trimethyl benzyl ammonium butoxide, sodium hydroxide, or sodium methoxide in the presence of a solvent, e.g. 1,4-dioxane, benzophenone or a large excess of the aldehyde.  Specified -CH=C&lt; containing group compounds are styrene, acrylonitrile, vinyl acetate, vinyl ketones, vinyl ethers, methyl methacrylate, isobutylene and maleic anhydride. Specifications 695,197, [Group XX], 713,947, 717,708, 717,710, 717,711, 717,712 and 732,602 and U.S.A. Specification 2,566,302 are referred to.

United States Patent PREPARATION OF POLYMER OF VINYL BEN ZAL ACETOPHENONE Cornelius C. Unruh and Charles F. H. Allen, Rochester,

N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application September 13, 1951, Serial No. 246,518

1 Claim. (Cl. 260-64) This invention relates to the preparation of polymers of vinyl acetophenone and more particularly to lightsensitive polymers of vinyl benzal acetophenones.

In the Allen et al. U. S. Patent application, Serial No. 771,142, filed August 28, 1947 now U. S. Patent 2,566,302, are described light-sensitive polymers made by the acylation of a polymer such as polystyrene with cinnamoyl chloride. Since acylation apparently proceeds to cre-on).-

a limited extent, a polymer is obtained such as one having the following formula:

0 G0 o-on=on Polymers obtained by this method in which the molecular ratio of unit A to unit B is from 5:1 to 18:1 (16 to 5 mol percent vinyl benzal acetophenone units) are said to possess especially useful photographic properties including solvent solubility and light sensitivity rendering the polymers particularly useful in photomechanical processes.

We have discovered that if polymers of the above type are prepared in the manner of our invention, they are not only more soluble in organic solvents but possess much higher sensitivity to light.

2,716,103 Patented Aug. 23, 1955 The preferred polymers of our invention are prepared by condensing a polymer of acylated vinyl benzenes and naphthalenes (i. e., ar-vinylacetophenones and ar-vinylacetonaphthones) with a benzaldehyde or naphthalde- 5 hyde. This is accomplished in several ways. A polymer containing aromatic nuclei such as a polystyrene or polyvinylnaphthalene or a copolymer threreof is partially or completely acylated by the Friedel-Crafts reaction and the resultant vinyl acetophenone polymer is then condensed with preferably, but not necessarily, an excess of the selected aromatic aldehyde of from about ,1 to about -50 mol of aldehyde per mol of polymer to yield the desired polyvinyl arylidene acetophenone. Alternately, a vinyl acetophenone, vinyl propionphenone, etc. compound can be homopolymerized or copolymerized with other compounds containing a polymerizable CH=C or CH2=C group, such as styrene, and the resultant polymer condensed with the aromatic aldehyde under consideration.

The following reactions illustrate methods of carrying out our invention:

ice

R represents a phenyl or czor fl-naphthyl group substituted or not with one or more groups such as o-methoxy, o-sulfo, o-hydroxy, o-chloro, etc. R represents a group such as hydrogen, alkoxy and aryloxy, e. g. o-methoxy, p-phenoxy, alkyl, e. g. m-tert-butyl and methyl, hydroxy, e. g. o-hydroxy, halogen, e. g. o-chloro, aralkyl, e. g. pbenzyl etc. The nucleus can be substituted with more than one of such groups, e. g. 3,4-dichloro, 2,5-dimethyl, 3,4-dihydroxy, 2,5-dichloro, 2,3dimethyl. Similarly the substituents may be present on a naphthalene nucleus when preparing the acylated vinyl-naphthone polymers. When the polymers reacted with the aldehyde or mixture of aldehydes, is obtained by acylation of a vinyl benzene or naphthalene polymer (methods I and III), the acid halide used may be any one of a mixture of those containing 2-5 carbon atoms such as acetyl, propionyl, butyryl and valeryl chlorides. Acetyl chloride is preferred since the vinyl benzalacetophenone and acetonaphthone polymers are more light sensitive than e. g. vinylbenzalpropionphenone polymers. Likewise, according to methods II and to the particular polymer under test.

IVI, the. carbon. c ainof the. ketone. group iof hew QQQ'.

'meric compound preferably contains 2-5 carbon atoms.

for preparing these ketones for, example from p-ethyl 'acetophenone. When .R"of1 the acylated compounds is amino, hydroxyl', sulfo and carboxyl, methods II and IV and the Williams procedure for preparing the ketone m'gnomers is used. In the formula in the above chart the values for the integers 11, 1 n" and n are dependent somewhat upon the molecular weight of the polymer reacted" with the aldehyde. n" in methods I andII and in 7 methods III. and; IV canibe positive integers, or equal to zero in, case of the acetyl groups of the polymer have been reacted with the aldehyde as shown in the fiXamples following. In the formula it wjllbe apparent that when a j mixture'of aldehydes including benzaldehyde is reacted with the acylated'polymer, the resultant polymer contains a mixture of vinyl aralacetophenone units.

When the polymers of our invention are obtained as described"; regardless of the derivation of the particular acylated polymer which is condensed with the aromatic aldehyde, the resultant products are in general more sensitive to light than those produced by the methods of the Allen et al. invention. son, sensitivity to light is determined by exposure of a layer of the polymer on a hydrophilic surface under a photographic step tablet to insolubilize thepolymer in the exposed regions. After exposure, the least-exposed areas are removed with a solvent for the polymer such as methyl ethyl ketone. The sensitometriccharacteristics of the'undissolved polymer remaining in the form of a step tablet are then recorded by well known photographic methods. From these values a speed val-ue is assigned, When tested by this method, representative polymers of the Allen et al."

invention possess speeds of'from 1.4 to 7 (made by;

reacting from 1:5 to 1:18 mols of cinnamoyl chloride per molof styrene polymer) whereas none of the polymers of our invention have speeds less than 7 and speeds of the order of "1000 to 8000 are readily obtained by selection of the proper reactants and conditions of reaction.

A possible explanation for the'fact that the polymers of our invention in general possess such relatively higher.

light sensitivity, lies partly in a belief that substantially no cross-linkfig& aneformed inthe polymers obtainedby 7 our methods. That is, it is believedthat when a polymer containing aromatic nuclei is cinnamoylated by ,themethods of the Allen jet al. invention, the cat lyst utilized 'induces the formation of cross-linkages which reduce light sensitivity and-Which tend toinsolubilize the polymet before very many cinnamoyl groups have been introduced into the molecule. On the contrary, by our methods we start from a polymer containing the desired proportion of vinyl acetophenone units. Subsequent reactionof the polymer with an aromaticaldehyde appears to yield a polymer substantially free of cross-linkages. Byour, methodswe readily obtain polymers containing at, least 2.1- mol .per cent of vinyl benzal acetophenone units-and such resinsapparent-ly due to the increased ofa .compou'nd having. the 1 general formula;

' wherein D represents an aryl group of the benzene or naphthalene fseries. substituted or not with groups, for

' example, alkyl, alkaryl, halogen, hydroxy, alkoxy, aryloxy, arn'ino, etc. as above indicated, and Q is a phenyl ortnaphthyl group substituted, or notwith for example In making this compari- V hea cunsa alloi talkoxy l hydroxyl. halogen. acetamiddalkoxy, aryloxy, amino sulfonic acid, etcl, as indicated above. V V

For example, polymers of the following are contemplated by our invention:

ot-naphthal acetylstyrene Isopropylbenzal acetylstyrene p-hydroxybenz al acetylstyrene p-dirnethylamino acetylstyrene o-chlorobenzal acetylstyrene p-acetamidobenzal acetylstyrene p-sulfobenzal acetylstyrene anisal acetylstyrene Veratral acetylstyrene- Anisal acetyl-o-methoxystyrene p-hydroxybenzal acetyl-mmethoziystyrene, o-chlorobenzal acetyl-o-chlorostyreneo-chlorobenzal acetyl-p-ben zylstyrene p-sulfobenzal acetyl-2,5-dimethylstyrene Anisal acetyl-p-phenoxystyrene. Anisal acetyl-p-bromostyrene 7 Tolual; acetyl-3,4-dimethoxystyrene Anisal acetyl-o-fluorostyrene Benzal acetyl-o-methoxystyrene Benzal acetyl-o-, m-, p-chlorostyrenes Benzal acetyl-o-, m-, p-bromostyrenes Benzal acetyl-p-benzylstyrene' Benzal acetyl-p-phenoxystyrene Benzal acetyl-3,4-dichlorostyrene Benzal acetyl-Z,S-dimethylstyrene Benzal a'cetyl-m methylstyrene Benzal acetyl-m-tert. butylstyrene Benzal acetyl-3,4-dihydroxystyrene Anisal benzal acetylstyrene Anisal methyl vinyl ketone Y The latter compound is representativerof other lightsensitive benzalacetyl and naphthalacetyl-group-containing polymers made by condensing aromatic aldehydes utilized similarly. Anisal benzal acetylstyrene is.representative of polymers obtained by reacting a mixture of aldehydes with the polymer containing acetyl groups.

Accordingly, the light-sensitive polymerscontain the a group.

in which n is a number from 1 to 4 and Q is an aryl h group of the benzene or naphthalene series (substituted: H

or not) and D is a single bond or aryl group of the benzene or naphthalene series. v V In general, the preferred polymers are obtained by condensing a polymer (homopolymer or copolymer) of a compound having the general formula:

CH2 =CH DZ C 3 wherein D is the same as above, in the presence of an alkaline, condensation catalyst, with a' benzaldehyde, the nucleusof which may contain jthe substituent of Q above. Preferably but not necessarily is used an excess of the aldehyde based upon the amount of vinyl acetophenone units present in the polymer molecule.

As the alkaline condensation catalyst are used the V quaternary ammonium bases such as trimethylbenzylammoniurn hydroxide, tetramethyl and .tetr-aethyl "amrentlyaredisclosed andclaimed comparable'methods for preparing vinylbenzal acetophenone polymers using an Other polyacid as the condensation catalyst which in general does not produce polymers of as high light sensitivity.

As described above, specific methods include acetylating either partially or fully, aromatic nuclei of a styrene polymer (homopolymer or copolymer) and then condensing acetyl groups thereof with a benzaldehyde or naphthaldehyde. Alternately, an acetylated styrene copolymer is obtained by copolymerization of a mixture of a vinyl acetophenone with a compound containing a polymerizable CH=O/ p, particularly a CH2=C/ group, followed by condensing acyl groups of the polymer with the selected aromatic aldehyde As will be apparent from the following examples given as illustrative of the methods of our invention, condensation with the aldehyde is preferably conducted in the presence of a diluent, which should be a solvent for both the vinyl acetophenone or acetonaphthone polymer and the aldehyde in use, such as 1,4-dioxane or ketones such as benzophenone, etc. It is particularly desirable to use as the solvent large excesses of the aldehydes in addition to the primary solvent, or, as shown in the examples, to use only the aldehyde reactant as solvent which increases the arylidene content of the polymer. It is advisable to use a diluent, otherwise in some cases the product tends to decrease in solubility during the course of the condensation. It is possible to employ as the diluent the original diluent used when making the vinyl acetophenone polymer or copolymer. That is, when vinyl acetophenone or acetonaphthone is homopolymerized or copolymerized with another polymerizable compound in a diluent, the polymer need not be isolated but the polymerization mixture can immediately be reacted with the desired aldehyde without removal of the diluent. Any unpolymerized monomer which may remain in the polymerization mixture does no harm when the condensation is subsequently carried out in its presence. As a source of the aldehyde for the condensation reaction may be used the pure aldehydes, or mixtures of two or more aldehydes can be used and the aldehyde may be furnished by an acetal, for example, a benzaldehyde acetal, or the diacetate may be used. These compounds readily decompose in the presence of the condensation catalyst to yield the corresponding aldehyde.

In the following table are tabulated the comparative speed values for polymers made by condensing various aldehydes with a selected vinyl acetophenone polymer:

* Vinylacetophenone (acetylated styrene).

Example 1.-Tlze preparation of polyvinyl acetophenone In an all glass vessel equipped with eflicient stirrer, dropping funnel and reflux condenser was placed 268 g. (2 mols) of finely divided anhydrous aluminum chloride and 1 liter of carbon disulfide. To the constantly stirred suspension was added 118 g. (1% mol.) of acetyl chloride followed by a solution of 104 g. (1 mol.) of polystyrene in 1 liter of carbon sulfide. Addition of the polymer solution took about minutes. The reaction mixture became warm and refluxed gently, with copious evolution of hydrogen chloride. No artificial heating or cooling was used. After about V2 hour the evolution of present.

hydrogen chloride had greatly diminished, but stirring was continued another hour. The reaction mixture was then filtered by suction, about 75% of the carbon disulfide used was thus recovered, and the residue on the filter consisted of highly swollen discrete particles. These were dried rapidly in a gentle current of air to give a dusty yellow powder, which was thoroughly agitated with cold 5% hydrochloric acid for about 15 minutes. The polymer was filtered off and washed by stirring in several changes of cold water. On drying at 4050 C. there was obtained 142-144 g. of fine, white powder of low ash content. The analysis of this product showed a carbon content of 81.9% and a hydrogen content of 6.9%. The calculated values for pure polyvinyl acetophenone are C=82.2%, H=6.85%.

The above polymer, proven to consist essentially of polyvinyl-p-acetophenone, may be further purified by dissolving it in acetone and pouring the colorless, slightly hazy solution into an excess of agitated water. The White, fibrous precipitate is again washed with water and dried. Found C=82.3%, H=7.0%.

The other acylated nuclear substituted styrene and vinylnaphthalene polymers indicated above are prepared in this manner from the appropriate styrene or vinylnaphthalene polymer. Also, these polymers can be obtained by polymerizing 0-, mand p-vinylacetophenones and acetonaphthones prepared by the methods of the Williams invention above.

Example 2.Condensati0n of polyvinyl acetophenone with aitisaldehyde Polyvinylacetophenone prepared as above was treated in a solution of an excess of anisaldehyde, with trimethylbenzylammonium hydroxide catalyst, for about 10 minutes followed by neutralizing the catalyst with acetic acid, precipitating and leaching the resin in ethyl alcohol. The product was light sensitive to a high degree.

Example 3.Condensati0n of polyvinyl acetophenone and p-dimethylamino benzaldehyde 5.0 grams of polyvinyl acetophenone were dissolved in a mixture of 10 grams of p-dimethylamino benzaldehyde and grams of benzophenone at 50 C. With the solution at 40 C. there was added to it 1.0 m. of 40% solution of trimethyl benzyl ammonium hydroxide with vigorous stirring. After exactly 3 minutes at 40 C. a slight excess of glacial acetic acid was added to neutralize the base present. The resulting solution was poured into an excess of stirred methanol and the yellow, rubbery polymer was redissolved in methyl ethyl ketone. The solution was now precipitated into excess alcohol. Finally the polymer was again dissolved in methyl ethyl ketone and poured into excess, agitated warm water. The yellow fibrous polymer was dried at room temperature. The polymer showed a speed of 10.

Example 4.Condensati0n of polyvinyl acetophenone and p-acetamino benzaldehyde 5 grams of polyvinyl acetophenone were dissolved in a mixture of 10 g. of p-acetamino benzaldehyde and 75 cc. of dried 1,4-dioxane. 1.0 g. of a 40% solution of benzyl trimethyl ammonium hydroxide were added. After exactly five minutes of stirring there was added a slight excess of glacial acetic acid to neutralize the base The solution was poured slowly into an excess of stirred methanol. The precipitate was again precipitated from methyl ethyl ketone into methanol and finally precipitated from methyl ethyl ketone into warm water. The white, fibrous polymer was dried at room temperature. The polymer showed a speed of 7.

Example 5 .Preparation of a copolymer of vinyl acetophenone and isobutylene grams of a copolymer of styrene and isobutylene (consisting of essentially equimolecular proportions of the' twe monomers) were dissolved in 1 liter of carbon disulfidej In a 5-1. flash fitted with an eflicient glass stirrer, condenser and dropping funnel "was suspended 1 '2 68 gqof anhydrous aluminum chloride in 'lliter of carbon-di'sulfide To this was then added 118g. of'acetyl chloride. While this suspension was-well stirred, the

. solution fof the polymer'was added over aperiod'of ten minutes. Copious 'evolution of the hydrogen chloride 'took'placeand a'lo'os'e 'bulky precipitate formed. After the addition'of the'po'lymer was complete, stirring 'was continued for another hour; The product was filtered V and the crumby polymer dried in acurrent of air. The

dried polymer was crushed up fine and'stirred up with an excess 'of'icecold 5% hydrochloric acid solution. The polymer was filtered ofi by suctionan'd 'w'ashed thoroughly' with water to remove excess a'cid. Dried at 40 C. Yieldabout'l80 grams.

Example 6. Conder1sati0n of 'a copolymer of vinyl acetpphenone and isobuty'lene with anisaldehyde The copolymer of Example'5 was dissolved in benz'ophenone or 1,4-dioxane and treated with'alkaline catalyst 'and'anisaldehyde as in Examples 3 and 4, to obtain a V light-sensitive solvent solublepolymer.

Example 7.-The preparation of monomeric vinyl acetophenone Polyvinyl acetophenone (prepared by the reaction of drous aluminum chloride, 'as'desc'ribed in the Kenyon et a1. U. S. patent application, Ser. No. 246,519, filed toncurrentlyherewith) was heated in 'a distilling appadisulfide wvere added dropwls i8- During this addition the reaction mixture 'soonfbeca'me thick and gelatinous and another500:cc. of carbondisulfide were added. Stirring wasconti'nued and more of the acid chloride mixture'was cautiously :added andsoon the gel structure collapsed and a suspensioniofihighly' swollen polymer particles suspended intheica'rbon'disulfide was obtained. The re- 7 .rn'ainder-of theacid chloride could now be" added at a poured slo'wly"intoianexcess of agitated methanol. The

V 'acetyl chloride on polystyrene in the presence of anhyratus'with the bare flame of a gas burner, the system be.-

7 ing-evacuated to'l mm. pressure. 85% yield of a light brown oil was obtained which-readily crystallized on chilling. This'product was :redistilled and avery pale yellow oil was-collected which distilled at 9398 'C. at 0.5 mm. Hg. pressure.

The distillate crystallized and this'was recrystallized twice from ligroin (B.'P. 60-9'0 C.) by chilling thesolution th'oroughly. White-crystalline plates were obtained which melted at 34 C. i Titration of a sample of'this for double-bond by means of bromine indicated a 98.9%

content of vinyl acetophenone;

The isomeric 'vinylacetopheno'nes and aceto'naphthones can al's o be prepared bythe methods of the mentioned 'Williams invention. Exa mple'8.The copolymerization "of'vinyl ucetophenbne fwith styrene H :5 'grams ofvinyl acetophenone-were mixed with 3.6 g.. of freshlydistilled styrene together with 0.043 g. of benzoyl peroxide and 25 cc. of methyl ethyl ketone.

- solution was refluxed gently on the steam bath for twenty-four hours. The resulting viscous, clear, colorless solutionwas poured into an excess of agitated methanol. Thefwhite,'friable polymer was leached in I fresh methanol,=then dried at 46 C. -Found=84.l%,'

. E i carr'lple"'Q.- Cridensali0n of copolymer ofstyr-ene aml Calculated C, 86.4%; H, 7.2%.

vinyl ac et ophenone with anisaldehyde T he copolymer prepared as above (Example 8') was mer. V V 'Example'10. The preparation of a partially acetyla'ted polystyrene 52 grams of'polystyrene were dissolved in "500 cc. of carbon .disulfide. This was 'added'to a suspension of 62 g. of anhydrous aluminum chloride in 500 cc. of carbon disulfide contained in a 3-liter glass flash fitted with an eificient glass stirrer condenser and dropping funnel. While the mixture was being vigorouslystirred, a mixture of 30'"g. -'0f acetyl chleridean'd {100 cc. jof carb'on condensed with excess anisaldehyde as in the previous examples to obtain a light-sensitivesolvent soluble polyfaster rate. nCopious evolution :of hydrogen chloride was observed and stirring was continued for another hour after the addition of the acid chloride was complete. The mixture was then filtered and dried in a current of air. The crumbly product was broken up fine and added to a well-stirred ice cold hydrochloricacid-solution. The white suspension was filtered ed and washed with water and dried. The white,-dry polymer wasdissolved in dioxane, the solution filtered and the filtrate was white, fibrous precipitate'was'washed thoroughly in'wa'ter,

then driedat 40C. 1

Example '11.C6nde fisdfidn of 21 partially acetylated polystyrene with Ivratrt'zldehyde Thepolymer offixample IOWas-cQndensed with ex-' cess veratraldehyde inra solution in 1','4-dioxane as in V the-foregoing examples to obtain; a -light-sensitive soluble resin. Example "1 2.''Alkqline condensation of'polyvinyl deem- Ip'henone 'w'iih 'benzaldehyde grams'of polyvinyl ac etophenone (Example l) were dissolved-in 190g; of;.benzaldehyde Three ml.;of a 40% solution of trimethyl benzyl ammonium hydroxide were mer was reprecipitated from methyl ethyl ketone solu: 7 tion by pouring it into excess ethyl alcohol. The nearly' white, fibrous precipitate was dried in the dark at room temperature. V

-Estimationof the degree of substitution by bromine absorption measurement indicated a value of 80.2%.

Sensitometric measurements indicated that it had a speed of approximately 8000. 1

Example Be-The condensation :of polyvinyl *acetophenom: with sodium o-sulfo-benzaldehyde 5 grams of polyvinyl acetophenone were dissolved ina mixture of '80 ccfof dioxane and cc. of alcohol. '10 grams of sodium o-sulfobenzaldehyde (the technical product was twice'recrys tallized from alcohol) were added to thestirred solution. "With efiicient stirring there was added to the slurry 20 'g. ofa solution'made up of one part by weight of a 40% solution of trimethylbenzyl hydroxide and 19 parts of. water.

showcloudiness. 5 cc. were added'to clear it, followed by'another 5 cc. 30"minutes later. a total oftwo hours at room temperature the solution was acidified-with a little acetic acid and poured into an excess of acetone. 'The precipitate was filtered'oifand redissolved in water containingalittle acetone. Again the solution 'was poured into excess -a'cetone. The precipitate was dissolved again in aqueousacetone and precipitated in excess acetone. The precipitate was then leachedin fresh acetone, filtered oil and dried in vacuo." The product w'as solublein -(by :weight): of V The addition. was made dropwise over=a period of 10 minutes. .The resulting solution was clear,'but after minutes it began to After. standing for acetone in water or a 30% solution (by weight) of alcohol in water. Speed:180.

Example 14.-Cndensation of polyvinyl acetophenone with B-naphthaldehyde Polyvinyl acetophenone prepared as in Example 1 was treated with excess fi-naphthaldehyde in 1,4-dioxane solution as in the previous examples to obtain a light-sensitive solvent-soluble polymer containing a high percentage of vinylnaphthalacetophenone units.

In analyzing the vinyl benzal acetophenone and acetonaphthone polymers for their content of benzal groups, two methods were used. The first involved titration of the double bond in the polymer with bromine. The second method which appeared to be most reliable in volved recording the spectral absorption in a spectral photometer at wavelengths 7.35 and 7.50 microns, using the absorption of the solvent pure chloroform for fixing the Io level. The analysis shown above was based on the latter method.

In addition to the vinyl acetophenone copolymers given in the above examples can be used acylated polymers of e. g. a-methyl-, m-methyl-, 2,5-dimethylor ethyl styrenes, o-hydroxy-, 0-, m-, p-chloro-, or bromo-, pbenzyl, 3,4-dichloro-, 3,4-dimethoxy-, m-tert.butyl-, styrenes, o-methoxy styrene, p-phenoxy styrene, etc., copolymers of mixtures of 5-95 mol per cent of these styrenes or of these styrene polymerized with polymerizable compounds such as styrene, acrylonitrile, vinyl acetate, vinyl ethers, acrylic and alkacrylic acids and esters, maleic anhydride, etc. The homologous vinyl propiophenone etc. polymers are of less value for the preparation of light-sensitive polymers. However, copolymers containing both vinyl acetophenone and vinyl propiophenone units are very useful in the invention. The Kenyon et al. invention above provides other acylated polymers which are useful in our invention.

In general, the polymer reacted with the aldehyde need only contain a selected proportion, 100 mol per cent or less, of the indicated --CO(CH2)11.1CH3 groups where n is 1 to 4. To this end the vinyl ketone polymers such as methyl vinyl ketone homopolymers or copolymers with other polymerizable compounds such as methyl methacrylate, are also useful. In this case the arylidene acetyl group obtained is attached directly to carbon chain of the polymer rather than indirectly as is the case when the aldehyde is reacted with polymers such as polyvinyl acetophenone.

Results similar to those of the above examples are obtained by condensing the benzaldehyde as above with homopolymers and copolymers of the o-, mand pacylated styrenes and vinyl naphthalenes prepared by the methods of the Williams invention. For example, substantially no diflerence in physical and chemical properties could be detected between the vinyl benzalacetophenone polymer of Example 12 and one obtained from p-vinylacetophenone (from p-ethylacetophenone) by condensation with benzaldehyde.

The polymers of the invention can be sensitized so as to further increase their sensitivity to light by use of the nitro compounds of Minsk et al. U. S. patent application Ser. No. 148,684, filed March 9, 1951, now U. S. Patent 2,610,120, and the triphenylmethane, anthrone, quinone and ketone compounds of the Minsk et al. applications Ser. Nos. 207,048-51, filed January 20, 1951 now U. S.

Patents 2,690,966, 2,670,285, 2,670,286 and 2,670,287, respectively, particularly those acylated vinyl benzene and naphthalene polymers having inherently low light sensitivity before sensitization, of the order of 100. Contrary to this, the light-sensitive polymers of the Allen et al. invention above are not sensitized by these compounds.

The polymers of the invention are particularly useful for photomechanical purposes where it is desired to prepare a resist image on a given surface. For example, the polymer is coated from solvent upon a support such as a metal plate, paper or organic colloid surface; for example, especially upon a surface which when moistened repels greasy printing inks such as a lithographic paper plate, and after exposure to the desired line or halftone subject, the unexposed areas are dissolved away, leaving a resist image on the original support. At this stage, if the resist has been formed on a surface repelling greasy inks when moistened, the element can be used directly as a printing plate. In other cases, the support, such as a metal plate, can be etched out in a well known manner to obtain an etched metal printing plate. Other uses for our polymers employing their light-sensitive properties will occur to those skilled in the art. For example, the polymers can be employed to form continuous or discontinuous soluble or insoluble coatings on any surface or object to which they will adhere, in the latter case exposure to light being employed to insolubilize the coating.

The light-sensitive polymers can be used for photographic reproduction of line, halftone or continuous tone subjects. In the latter case it is preferable to coat the polymer on a transparent support, expose the coating through the support followed by washing away the least exposed areas with solvent leaving a continuous tone relief image on the support which may be colored previously or subsequently with subtractively colored dyes or for purposes of color photography. Three such subtractively colored reliefs corresponding to blue, green and red aspects of a subject can then be superimposed to obtain a natural color reproduction or three such images may be formed on a single support by successively coating layers of the polymers on the support after first forming relief images thereon corresponding to one or more of the red, green, or blue aspects of the original References Cited in the file of this patent UNITED STATES PATENTS DAlelio June 1, 1943 Brubaker Feb. 8, 1944 OTHER REFERENCES Fieser et al.: Organic Chemistry, Heath & Co., 1950, pages 714 and 715.

Coombs et al., I our. Chem. Soc. 1940, pages 1295-1300. 

